Electropolish interrupter



Aug. 21, 1951 E. H. WALLACE ELECTROPOLISH INTERRUPTER 2 Sheets-Sheet 1 Filed Feb. 27, 1948 w fix an N m 7 .Q\ m E W tmtkumk [El/671E507 58 20021215. W16 lace f 1 Aid z;

y MMYW 2 Sheets-Sheet 2 Filed Feb. 27, 1948 fiwezzior fi alaaarafima Patented Aug. 21 1951 ELECTROPOLISH INTERRUPTER Edward H. Wallace, Sherrill, N. Y., assignor to Oneida, Ltd., Oneida, N. Y., a corporation of New York Application February 27, 1948, Serial No. 11,703

4 Claims.

This invention relates to the control of an electrolytic cell and more particularly to a cell as used for electropolishing operations-as in the polishing or polishing and plating of silverware.

It is known to the art that a high luster is developed by the surface of a metal object, which has been immersed in an aqueous electrolytic bath of an alkali metal cyanide as the anode, and subjected for a sufiicient length of time to an electrical potential which is maintained between the point at which the metal surface manifest a polishing effect and that at which a spontaneous flashing phenomena, occurs (U. S. Patent 2316294) February 25, 1947.

However, practical difficulties are encountered, especially in a large installation with a high current flow through the cell, when an attempt is made to maintain the potential of a low voltage high current Supply within such narrow confines of the polishing voltage range. been proposed to obtain a polishing action by intermittently applying power to the metal electrodes for a few seconds. After the power is interrupted, it is then sent through the cell again and this intermittent operation repeated for several cycles until the desired luster is attained.

Objects of this invention are to provide an electric circuit which reduces the voltage of the power-supply of an electrolytic cell when such voltage has risen to a predetermined value op- Another object is to provide an electric circuit which reverses the polarity of the cell power source when the voltage has risen to a predetermined value optimum for the conditions of cell operation and which thereupon is effective to restore the original polarity after a predetermined time delay.

It is also an object that the circuits should operate automatically and with a minimum of attention, require very little maintenance, and be simple to install and economical to construct. Other objects will appear from the following disclosure.

In a broad aspect the invention contemplates an electrical circuit for controlling the power source for supplying to the electrodes of an electrolytic cell, a potential varying with the load placed upon the source by the cell. In different aspects the switch is used to vary the potential, change the polarity or disconnect the potential Recently it has supplied to the electrodes. The increase in resistance between the electrodes accompanying the electrolytic action reduces the current supplied by the power source thereby effectuating a change in the potential of such source. When the power source potential reaches a value predetermined as optimum for the conditions of cell operation, a voltage sensitive device such as a tube or relay is actuated thereby to complete a control circuit through the circuit making elements of the device, to operate the switch element in the cell power source circuit. After the lapse of a time interval sufiicient to depolarize the cell substantially, a timing device interrupts the control circuit so that the switching element returns to its normal position and either restores the original potential supplied to the electrodes by the power source or reverse the polarity thereof.

In a more specific aspect the invention contemplates controlling such a power source for the electrodes of the electropolishing cell by the use of a relay having normally closed contacts operated by a solenoid to disconnect the electrodes of the cell from the source. The solenoid is connected in series with the plate circuit of a vacuum tube. The cathode and grid of the tube are connected respectively to the cell cathode and anode so that the electrode potential difference therebetween is impressed upon the grid of the tube. When, as described above, the internal resistance of the cell increases and the potential of the power source reaches a predetermined value corresponding to the tube firing potential, the tube conducts. The resulting current flow in the plate circuit energizes the solenoid thereby to close the contacts and disconnect the cell from the power source. Also connected in the plate circuit of the vacuum tube is a normally closed switch operated by a timing device. After the lapse of a time interval sufficient to depolarize the cell substantially, the switch is opened by the timing device, the relay solenoid is de-energized and itscontacts return to the normally closed position to restore the original potential to the electrodes.

In another specific aspect of the invention in which both polishing and plating of the surface is to be effected, a double pole, double throw relay is connected between the electrodes of the cell and a direct potential power source, the potential of which varies with the load imposed by the cell. The relay contacts are connected so that the polarity of potential supplied to the cell electrodes from the power source is reversed when the relay is energized. The relay solenoid is connected in series with the plate circuit of a vacuum tube.

The cathode and grid of the tube are connected respectively to the cell cathode and anode to imress the electrode potential difference upon the grid of the tube. When as a result of increased internal cell resistance the potential of the power source reaches a predetermined tube firing potential, the tube conducts. The resulting current flow in the plate circuit energizes the solenoid to move the contacts and reverse the polarity of the potential supplied to the cell electrodes, whereby a plating action takes place in the cell. Also connected in the plate circuit of the vacuum tube is a normally closed switch operated by a timing device. After the lapse of a time interval sufficient to depolarize the cell and to effect a predetermined amount of plating upon the surface of the work in the cell the switch is opened by the timing device. The relay solenoid is deenergized and its contacts return to restore the original polishing potential polarity to the electrodes.

For the purpose of illustration, a typical embodiment of the invention is shown in the accompanying drawing in which:

Fig. l is the circuit diagram of one embodiment of the invention whereby the cell electrodes are disconnected from the potential source; and

Fig. 2 is a circuit diagram of another embodiment of the invention whereby the polarity of the potential source connected to the cell electrodes is reversed.

In the particular embodiment of the invention chosen for the purpose of illustration, the two cathodes I2 and a metal article, such as a silver plated spoon with 8 square inches of silver plated surface to be polished, are immersed in an electrolytic cell I3 containing an aqueous electrolytic bath I5 of an alkaline metal cyanide, for example, a 3 liter bath comprising 0.3 molar silver, 0.3 molar potassium carbonate and 0.3 molar free potassium cyanide.

The plated article serves as an anode II of the cell I3 and is connected by a cable Iii to a positive terminal I ia. of the output circuit of a power rectifier II with an output rating of 50 amperes at '7 volts D. C. A silver. cathode I2 with an area of 14 square inches is placed on each side of the anode II with a distance of 4 inches therebetween. The cathodes I2 are connected with a negative terminal I 6a of the rectifier output circuit by a cable IS. The anode II is agitated between the cathode I2 by any conventional means at the rate of 1.4 ft./min.

The input circuit of the rectifier I! is connected by a lead I9 to a grounded terminal 0 of an alternating power source (not shown). The input circuit is completed to a terminal a, of the power supply through a wire I8, the normally open contacts 2| and 22' of a relay sI and a wire 20.

Also connected with the anode and cathodes II and I2 is a voltage sensitive device, such as a gas filled vacuum tube G which may be of the 2050 type. The anode II of the cell I3 is connected by means of a wire 23 to a terminal m which is linked to a grid gI of the tube G. A tube cathode with a terminal n is connected to the cathode I2 by a wire 26. A capacitor CI and a resistor 1'I are connected in parallel across the terminals 'm and n. The capacitor CI prevents the premature firing of the tube G the instant current is supplied to the cell electrodes, and also tends to filter out any hash or 60 cycle ripple which may be present. The resistor rI provides a return circuit for the grid gI. A plate p of the tube G, which together with the cathode f comprise the circuit making elements of the tube G, is connected to a positive terminal 41 of a conventional direct current power supply P through a coil 21 of a relay s2, and the contacts 32 and 33 of a switch s3 controlled by a timing device T, for example a conventional vacuum tube time delay relay.

The terminal 0 of the direct current power supply P is grounded. The potential to ground of a grid 92 of the tube G and therefore the firing potential of the tube is controlled by the position of an adjustable tap 34 of a resistor 12 which is connected between the grounded terminal 0 and the tube cathode f. A bleeder resistor rb is connected between the terminal cl and the tube cathode f.

The timing device T for operating the contacts 32 and 33 of the switch s3 comprises a vacuum tube V such as the type 6C5 with a plate p3 connected by the wires 36 and 3'! with a coil 38 of the relay s3 and a terminal 35 at one end of a winding of an autotransiormer H. The terminal 39 at the opposite end of the autotransformer winding is linked with the ground terminal 0. The power supply circuit to the winding of the autotransformer t! is completed by connecting the terminal a with an intermediate tap 4 I. The tube cathode f3 of the tube V is connected to the grounded terminal 0 through a tapped resistor r3. One tap M of the resistor r3 is linked with an intermediate tap 42 of the autotransformer tl by a lead 45.

A timing capacitor C2 is connected between a second adjustable tap 43 of the resistor 13 and a control grid 93 of the tube V. A resistor 1-4 is connected in parallel with the capacitor C2 to act as a bleeder for any accumulated charge. The tube cathode f3 is also connected by a wire 46 with a stationary contact 28 of the relay 52. A moving relay contact 30 is. grounded to the terminal 0 so that the energizing of the relay s2 places the tube cathode f3 at ground potential. A second terminal 29 of the relay s2 is connected by the wire 47 to one end of a coil 23 of the relay SL The other end of the coil 23 is connected to terminal a through the wires 25 and 20.

In Fig. 2 is shown another embodiment of the invention wherein the power supplied to the anode II and the cathodes I2 from the rectifier I1 is reversed in polarity by the energization of a reversing relay sI I. The relay sI I comprises an actuating coil I23 and two movable contacts 53 and 63. When the coil I23 is energized, the movable contact 53 bridges a pair of stationary contacts 52d and 53a; and the movable contact I53 bridges a pair of stationary contacts 62a and 6401.. In the de-energized relay position a pair of stationary contacts 52b and 54b and a pair of stationary contacts 621) and MD are connected by the movable contacts 53 and 63 respectively.

A resistor r5 links the contacts 52a. and 62b. The stationary contacts 52b, 54b and 64a are connected to the stationary contacts 62a, 54a and 33b respectively. The terminals I la, and I60, of the output circuit of the rectifier I! are joined to the stationary contacts 52a and 62a. by the cables 5I and 6| respectively. The terminals 54a and 64a are connected to the anode II and the cathodes I2 by the cables 55 and 35 respectively. The remainder of the circuit is similar to the circuit shown in Fig. 1 and desoribed'in detail heretofore.

The silverware to be polished is suspended in the electrolyte I5 and the alternating current power source is connected across the terminals a and c. The coil 23 of the relay sI is energized fromthe power sourcebya circuit through the wires-20, 25 and 41 andithe contacts 29 and 30 of the relayes2'. Energization of coil 23 closes the contacts 21- and 22 to energize the rectifier I? having a rated output capacity of'50 amperes at 7: volts D. C. and supply a potential across the anode II and the cathodes I2 of the cell I3. The resultingcurrent' flow causes a complex electrolytic action which dissolves the high spots upon the anode: surface. As. the electrolytic action takes place, the internal resistance of the cell increases so that after approximately. for example 4 secondsv the voltage difference between the anode I I and the cathodesl 2 has increased to for example 2.8 volts.

The adjustable tap 34ofthe resistor T2 is acljusted so that'the potential on the grid 92 is such that when a voltageof for example 2.8 volts appearsbetween-the grid gl and the filament f, the tube G will conduct. After the voltage differonce-between the anode and the cathodes I2;

reaches thi predeterminedpotential as described above, the resulting current flow from the direct current supply P through the coil 21 of the relay s2 opens the contacts 23 and 30 to de-energize the coil 23of the relay sl. The contacts 2| and 22 open to-de-energize the rectifier II stopping the polishing action.

The connectionof an alternating power source across the terminals a and c energizes the wind- 3 ing of the autotransformer tI. The resulting voltage difference between the tap 42. and the grounded terminal 39 of the autotransformer tI circulates an alternating current through a path including the wire 45and the portion of the re sistor r3 between the tap 44 and the terminal. grounded c. During'the portion of each cycle when the plate p3 is negative with respect to the tap 44, the tap 43 and thereforethe grid'gB are positive with respect to the tap M'and'the fila ment f3 by the'amount'equal to=thevo-ltage difference in the resistor r3 between the taps 43 and 44. With the contacts Hand 36 open a current flows through a circuit including the tube cathodef3, the-grid'g3, the capacitor C2, the tap 43 and the resistor T3 to build up a charge on the capacitor C2 so that-the gridg3v isat a negative average potential; As the relative characteristics of 'the resistor T4 and the capacitor C2 are such that the latter does: not discharge appreciably during the portion of the cycle when the polarity is reversed, the grid g3 is maintained at substantially the same negative potential and tube V does not conduct.

When, however, the contacts 28 and 3e are closed by the energization of the coil 21, the cathode I3 is connected to ground through the lead 46 so that the tap 43 is positive with respect to the tube cathode f3 by the amount of the voltage difierence in the portion of the resistor r3 between the adjustable tap 43 and ground during the portion of the cycle when the plate 233 is positive with respect to the cathode f3. The capacitor C2, however, retains a negative charge which opposes the positive voltage between the tap 43 and ground and prevents the conduction of the tube V. After a time delay determined by the characteristics of the capacitor C2 and the resistor T4, the negative charge upon the capacitor C2 discharges through the resistor r4 until the negative voltage upon the grid 93 has decreased sufficiently so that a current of suflicient magnitude to energize the coil 38 of the relay s3 flows through the tube V thereby opening the contacts 32 and 33.

The size of the capacitor C2. and the resistor T4. are chosen so that the tap 43 can be adjusted to obtain a delay of for example approximately 4 secondsbefore the tube V conducts. When the resulting flowof-current through the plate circuit ofthe tube. V energizes the coil 38 of the relay s3, the opening of the normally closed, contacts 32 and 33 interrupts thedirect'current supply P to the relay coil 21. The-de-energization of the coil 21 closes the contacts 29 and 30 to energize the rectifier II andopens, the contacts 23 and 30 so that the grid 93 cuts off thev current flowing through the tube V and the relay 33 to reclose the contacts 32 and 33. thus resetting the timing device T. The 4-second power on and ofi cycles are repeated as described above fOr a total elapsed on period of approximately 1 minute which in the present example produced a satisfactory luster.

In the embodiment shown in Fig. 2, the polarityof the power source isreversed so that silver from the. electrolyte l5.in the cell I3 is plated upon the surface of the anode I I after the film is reduced. The connecting of an alternating power source to the terminals a and c energizes the coil I23, of the relay ,9] I, the rectifier I1 and the autotransformer. tl. The moving contacts 53 and 53 connectthe anode I I and the cathodes 12 of acell I3 to the rectifier output terminals Ma. and Ifia respectively. A film is formed and after in the present example approximately 4 seconds of operation the predetermined potential difierence of. 2.8. volts appears across the anode H and the cathodes I2. The tube G conducts so that the relay s2 is energized and the relay sit is de-energized in a manner similar to that described heretofore. The contacts 53 and 53 move to reverse the polarity of the power supplied to the electrodes of the cell I3. The rectifier terminal Ma is connected tothe cathodes I2 by means of the cable 5|, the resistor r5, the contact 62b, the moving contact '63, the contact 54b, and the cable 65. The rectifier terminal ISa is connected to the anode I I by the cable GI, the contact.52b, the moving contact 53, the contact 55b-, and thecable 55.

The voltage difference through the resistor r5 reduces. the rectifier-voltage applied across the anode II and cathodes I2 to that suitable for silver plating, for example, 2 volts. The tap 43 of the resistor T3 of the timing device T is adjusted to de-energize the relay 8H and limit the plating time to for example 15 seconds. The polarity of the power source is then again reversed to eflect the polishing action. This cycle is repeated for approximately 30 minutes of total plating time to effect a satisfactory thickness of plate.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall Within the scope of the appended claims.

I claim:

1. An electric circuit for controlling a direct power source supplying to the electrodes of an electrolytic cell, a potential varying with the load, said circuit comprising a coil actuated reversing relay for connecting the power source to the cell electrodes, a vacuum tube having a plate, a cathode and a grid, said cathode and grid being connected respectively to the cathode and anode of said cell so that the voltage difference between the anode and cathode of the cell is impressed upon the grid, said plate being connected in series with the actuating coil of the reversing relay to energize the reversing relay when the potential difference between the anode and cathode of the cell reaches a value which will cause the tube to conduct, and a timing device having a switch interposed in the circuit of the plate and the coil to deenergize the reversing relay and reconnect the anode and cathode of the cell with the original polarity after the elapse of a time interval from energization of the solenoid suincient substantially to depolarize the cell.

2. An electric circuit for controlling a power source for supplying to the electrodes of an electrolytic cell a potential varying with the load,

said circuit comprising a coil actuated reversing relay for connecting the power source to the cell electrodes, a voltage sensitive device having a circuit making element rendered conducting in response to a voltage change connected across the electrodes so that the voltage difference due to polarization is impressed upon the device, the circuit making element of said device being connected in series with the actuating coil of the re versing relay to operate the reversing relay when the electrode voltage difierence reaches a preselected value, and a timing device having a switch interposed in the series circuit of the circuit making element and the coil to operate the reversing relay to restore the original polarity after the elapse of a time interval from the impressing of the selected polarity sufficient substantially to depolarize the cell.

3. An electric circuit for controlling a direct power source supplying to the electrodes of an electrolytic cell, a potential varying with the load, said circuit comprising a coil actuated reversing relay movable between two positions for connecting the power source to the cell electrodes with either polarity, a resistor connected in series with the cell electrodes in one position of the re lay, a vacuum tube having a plate, a cathode and a grid, said cathode and grid being connected respectively to the cathode and anode of said cell so that the voltage difierence between the anode and cathode of the cell is impressed upon the grid, said plate being connected in series with the actuating coil of the reversing relay to operate the reversing relay thereby to apply a lower voltage of opposite polarity to the anode and cathode of the cell when the potential diifer- 8 ence therebetween reaches a value which will cause the tube to conduct, and a timing device having a switch interposed in the circuit of the plate and the coil to deenergize the reversing relay and reconnect the anode and cathode of the cell with the original polarity after the elapse of a time interval from energization of the solenoid sufiicient substantially to depolarize the cell.

4. An electric circuit for controlling a power source for supplying to the electrodes of an electrolytic cell a potential varying with the load, said circuit comprising a coil actuated reversing relay movable between two positions for connecting the power source to the cell electrodes with either polarity, a voltage reducing element connected in series with the cell electrodes in one position of the relay, a voltage sensitive device having a circuit making element rendered conducting in response to a voltage change connected across the electrodes so that the voltage difference due to polarization is impressed upon the device, the circuit making element of said device being connected in series with the actuating coil of the reversing relay to operate the reversing relay thereby to apply a lower voltage of opposite polarity to the cell electrodes when the electrode potential difference reaches a preselected value, and a timing device having a switch interposed in the series circuit of the circuit making element and the coil to operate the reversing relay to restore the original polarity after the elapse of a time interval from the impressing of the selected polarity sufficient substantially to depolarize the cell.

EDWARD H. WALLACE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,428,049 Nickum Sept. 5, 1922 1,534,709 Holt Apr. 21, 1925 2,470,741 Gordon May 17, 1949 FOREIGN PATENTS Number Country Date 603,910 Germany Oct. 11, 1934 

